RE: [Chrysler300] Surprising source of miss in 300 ?
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RE: [Chrysler300] Surprising source of miss in 300 ?

Hi Mike, A bad ballast resistor would stop you ---not burn the points. Remember Darts that start , and then stall immediately when you release key? Ballast. I believe you may possibly have a wiring mistake at the ballast where the feed to the coil is taken on the 12v side, or something like that .Check all connections , colors of wires at and  around ballast and on back of key and at coil,  to factory wiring diagram. It will sort of work with 10 different mistakes..particularly confusing on these cars is Chrysler's start system, which kills ignition loads at crank except for a new feed --only during crank  ---you get from the second S terminal (or sometimes another relay contact on the starter relay) ------that allows the car to start while  the normal ignition power wire feeding the ballast is dead, zero v or very low (it back feeds some though ballast into ign power wire ) . I think they did this so all other loads go off during crank (ac, radio, heat fan  etc) , but then it would not catch as there is no main ign power, by design --unless the 12V is supplied..they supply it directly to the coil, bypassing the ballast  during crank from that second S terminal on  key , You cannot do it with the same S terminal as the starter,  or else ballast volts normally there running will pull in the starter relay all the time the ign is on. 

This whole thing can drive you crazy and is not well explained . I only know about it after suffering with two swapped wires on a Dart key switch. Plug had melted someone made up individual wires then put them on,  swapping two...long story, not for here. Car ran.

While idling you should have like 5-6 V at coil input side w average meter , ---or at least ,  less than the 12V (varies w RPM dwell etc) , if wiring right..

If not that wiring issue,  burned points also immediately says bad capacitor, especially if a "new one". If it has stamped indented lines in can end , opposite end from the wire going in, it is Chinese junk. Get an old one, check it, put in  . Car will barely run with no capacitor or an open one, spark extremely weak and arcing points at break. . It will however run OK initially with 12V on coil (the wiring error) --- but eventually burn points. 

Dwell going UP (if that is correct data) is points way set too close , Mike ...Burning , you would expect an opening up, Dwell drop, unless cam rub block is rubbing down? And so not opening them. Look at the mechanical action with the cap off... There is chance points were set too close, does not matter who did it,  did not open enough, they arc across and burn. Or same thing caused by open capacitor. I had mentioned in an earlier email how critical that setting process is ,and hard to get perfect. 

Sounds like bad cap..They are intermittent too. Adds to the fun.

-----Original Message-----
From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Michael Moore mmoore8425@xxxxxxx [Chrysler300]
Sent: Friday, March 04, 2016 9:55 AM
To: Mike Moore
Cc: Chrysler300@xxxxxxxxxxxxxxx
Subject: [Chrysler300] Surprising source of miss in 300 ?

I have been trying to eliminate a miss in my 300H. 

In the ongoing effort, I have replaced the damper, installed a Philbin rebuilt distributor, new plug wires, new plugs, carbs “restored”, coil replaced etc.  with no improvement. Even 108 octane gasoline hasn’t helped.

 I made arrangements for a visit to a  great shop with a Sun engine analyzer (equivalent) , but I had to get it running reliably enough to get down there, and it now ran worse each time I started it. 

 Judging the problem to be ignition related versus carbs, I decided to strip and replace the entire ignition apparatus from ballast resistor through plugs.  I  ordered  NOS Champion J-12Y plugs (which have always worked well for me), a new set of ignition cables (which are the best I have seen), a new coil, correct Mopar points,  and new capacitor. 

I began with a new correct ballast resistor and noticed  the old ballast resistor ceramic  wire wound resistor inside was broken into two pieces. As I  hadn’t disassembled the rest of the system, I started the car with the new ballast resistor with no improvement, so I incorrectly dismissed that as the source of my miss. 

While waiting for my original new parts to arrive, and after doing a thorough (165# on all 8) compression check   (because all the plugs were out, front wheels were off and access was so easy),  I disassembled the points from the distributor last night. 

I found them badly burned! Aha!
 My earlier distributor trouble shooting was to check only the dwell angle since it had recently been rebuilt. I noted the dwell angle had increased to 45 degrees since I installed the distributor when it came back from Philbin.  

I now believe what happened was that the ballast resistor failed sometime in past years, allowing the points to burn because of the higher than specified voltage on the coil. In recent years I haven’t driven the car much, but have changed the points entirely too often and haven’t noticed it too much because although it might be only 1500 miles,  it may have been 3 years. I am certainly anxious to get it back together.

Thanks for all the help on line and off.
Mike Moore

Posted by: Michael Moore <mmoore8425@xxxxxxx>

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Posted by: "John Grady" <jkg@xxxxxxxxxxxxxxxxx>

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